GaN transistors can withstand extreme heat and are capable of handling power levels at frequencies well beyond those possible with silicon, gallium arsenide, or essentially most of the other semiconductor yet fabricated. However, no inexpensive substrate material for gallium nitride exists. A big contributor to the high price of the best devices now is the cost of silicon carbide substrate. GaN high electron mobility transistors (HEMT) grown on silicon substrate, which combine the merits of high performance and lost cost, are studied in this thesis....[ Read more ]

GaN transistors can withstand extreme heat and are capable of handling power levels at frequencies well beyond those possible with silicon, gallium arsenide, or essentially most of the other semiconductor yet fabricated. However, no inexpensive substrate material for gallium nitride exists. A big contributor to the high price of the best devices now is the cost of silicon carbide substrate. GaN high electron mobility transistors (HEMT) grown on silicon substrate, which combine the merits of high performance and lost cost, are studied in this thesis.

The greatest challenge with GaN grown on silicon is to manage the large thermal mismatch. To solve this problem, the substrate patterning scheme was proposed. Crack-free GaN film can be obtained and the device on the patterned region has improved DC and RF performance. This approach provides a robust way to extend GaN growth on large size substrate.

Although excellent performance has been achieved on A1GaN/GaN HEMT, most of the efforts have been directed towards D-mode device. In this work for the first time we implemented the E-mode HEMTs on silicon substrate with a novel approach proposed by our group. The fabricated devices were characterized in detail and showed desirable performance. The integration of D/E HEMTs on low-cost silicon substrate could open potential applications for high temperature digital ICs.

The A1GaN/GaN HEMTs are usually plagued with current collapse and large gate leakage problem. Using Si₃N₄ as the insulator, the fabricated MISFET devices demonstrate reduced gate current and better RF performance. Therefore, the MISFET is a viable alternative to HFETs for high-power, high-temperature RF applications.